Fluid control is routinely practiced within a wide variety of industries. Control is typically achieved using devices that are specifically designed to perform a unique control operation. Examples of such control devices are pressure relief valves, pressure regulators, back-pressure regulators, velocity fuses, mass flow controllers, pilot operated valves, check valves, and shuttle valves.
Pressure is typically communicated from one source to another via the flow of gas or liquid. Operational challenges arise when the flow used to communicate pressure is laden with particulates. These particulates introduce the potential for a device to lose functionality as a result of solids becoming lodged in a device's moving parts, as well as damage resulting from the cutting capacity of high velocity, particle-laden fluid streams passing over a device's sealing components. The use of rigid seal materials such as metal or thermoplastics enhance the durability of a device, but compromise the sealability of the device.
For example, a steel ball could never seal a circular steel aperture if a sand grain was wedged between the steel ball and the edge of the aperture (or if the edge of the aperture was slightly nicked). If the ball was made of a pliable material such as rubber, the ball could seal the circular aperture because the sand grain could imbed in the ball and the ball could then fully contact the perimeter of aperture. While the rubber ball is a superior sealing material, it is also highly susceptible to damage from the cutting action of high velocity fluid streams.
Many valving designs directly, or indirectly, involve three pressures: 1.) inline high pressure source; 2.) inline low pressure source; and 3.) a static pressure source, e.g., ambient pressure in a spring cavity. Valve designs that involve an isolated, or sealed, static pressure exhibit limited functionality in a downhole environment. The primary reason is that most downhole operations are performed in a well that is filled with liquid, thus the static pressure increases as a function of depth. This change in static pressure results in a change in valve performance as a function of depth. Valve designs that provide free static pressure communication to all actuating parts within the system enable depth (or static pressure) independence. This is because fluid based valve actuation forces result from differential pressures acting upon an area. Since the actuation forces are based on the difference between pressure sources, the reference pressure (or static pressure) that is common to all sources is canceled out, and the performance of the valve becomes depth independent.
An additional criteria required of downhole fluid control operations is related to size. Wellbores of various diameters are created in an effort to optimize the economic impact of a field development; and valves must be smaller than the wellbore diameter in which they are deployed. As a result, valves with small external dimensions possess a larger portfolio of accessible intervention wells than larger valves of similar function. In addition, when valves are deployed downhole they are not readily accessible for servicing; thus significant expense is typically incurred if valve failures occur during an intervention program. This emphasizes the need for downhole valves to be highly reliable.
For various applications, certain advantages can be realized by designing a control valve device in the form of a cartridge valve. A cartridge style control valve offers the following benefits: 1.) the ability to interchangeably deploy the same valve in multiple tools that require the given valve's control function; 2.) the ability to incorporate the valve into cartridge valve based logic systems; 3.) the ability to verify functionality before deployment by performing bench-top surface testing of the valve; 4.) simplified valve replacement and servicing; and 5.) cartridge valves are well suited for deployment in parallel, or series (e.g., for the purpose of redundancy in safety critical applications).
Most downhole fluid control devices are deployed as a single unit or connected in series with other downhole components. The systems are generally comprised of a combination of annular based components, springs, and/or balls. Annular based components are defined as parts that are symmetric about the centerline of the valve. The valves tend to have rigid seal materials and are designed in a fashion that are susceptible to compromised functionality due to particulate bridging between the rigid seal materials. Current technology does not provide a suitable physical design, or design concept for the problem.
A need exists for small cartridge-style fluid control devices that are static pressure independent and capable of repeatable, reliable, particulate insensitive performance in service conditions typical of downhole intervention environments. An object of this invention is to provide such fluid control devices. Other objects will become apparent through consideration of the following specification together with the accompanying drawings.